11. Which of the following statement is not true for a hole?

1. 1. Holes may constitute an electric current

   
   
   

   2. Holes can be considered as a net positive charge

   
   
   

   3. Holes can exist in any material including conductors

   
   
   

   4. Holes can exist in certain semiconductor materials only
      

   
   
   

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   NA

   Correct Option: C

   NA

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12. Fermi level for an intrinsic semiconductor lies—

1. 1. Near valence band

   
   
   

   2. Near conduction band

   
   
   

   3. Middle of valence and conduction band

   
   
   

   4. Can lies anywhere

   
   
   

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   Fermi level for an intrinsic semiconductor lies middle of valence and conduction band.

   Correct Option: C

   Fermi level for an intrinsic semiconductor lies middle of valence and conduction band.

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13. Which of the following can be determined by using a Hall crystal?
    1. Concentration of holes in a p-type semiconductor.
    2. Concentration of electrons in an n-type semiconductor.
    3. Temperature of a the set-up with any type of semiconductor.
    4. Diffusion constant and life-time of minority carriers of any type of semiconductor.
    Select the correct answer using the code given below:

1. 1. Only 1 and 2

   
   
   

   2. 1, 2 and 4

   
   
   

   3. Only 3 and 4

   
   
   

   4. Only 2 and 4

   
   
   

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   Hall effect is used to determine whether a semiconductor is n-type or p-type and to find the carrier concentration. Hence alternative (A) is the correct choice.

   Correct Option: A

   Hall effect is used to determine whether a semiconductor is n-type or p-type and to find the carrier concentration. Hence alternative (A) is the correct choice.

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14. In a Hall effect experiment, a p-type semiconductor sample with hole concentration p₁ is used. The measured value of the Hall voltage is V_H1. If the p-type sample is now replaced by another p-type sample with hole concentration p₂ where p₂ = 2p₁. What is the net Hall voltage V_H2?

1. 1. 2V_H1

   
   
   

   2. 4V_H1

   
   
   

   3. (1/2)V_H1

   
   
   

   4. (1/4)V_H1

   
   
   

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   We know that hall voltage is inversely proportional to the concentration i.e.,
   

   VH	1
   	Concentration

   
   

   Therefore,		VH1	=	P2
   		VH2		P1

   
   

   Therefore,		VH1	=	P2
   		VH2		P1

   
   

   or VH2=		P1	x VH1 =	1	VH1
   		VH2		2

   
   Hence alternative (C) is the correct choice.

   Correct Option: C

   We know that hall voltage is inversely proportional to the concentration i.e.,
   

   VH	1
   	Concentration

   
   

   Therefore,		VH1	=	P2
   		VH2		P1

   
   

   Therefore,		VH1	=	P2
   		VH2		P1

   
   

   or VH2=		P1	x VH1 =	1	VH1
   		VH2		2

   
   Hence alternative (C) is the correct choice.

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15. An intrinsic semiconductor with energy gap 1 eV has a carrier concentration N at temperature 200 K. Another intrinsic semiconductor has the same value of carrier concentration N at temperature 600 K. What is the energy gap value for the second semiconductor?

1. 1. (1/3) eV

   
   
   

   2. (3/2) eV

   
   
   

   3. 3 eV

   
   
   

   4. 9 eV

   
   
   

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   Given E_g1 = 1_eV, T₁ = 200 K, T₂ = 600 K, E_g2 =?
   

   Eg1	=	T2
   Eg2		T1

   
   Where Eg = Energy band gap
   T = Temperature
   

   Now, Eg2 = Eg1 ×	T1
   	T2

   
   

   = 1eV ×	200 K	=	1eV
   	600 K		3

   
   Hence alternative (D) is the correct choice.

   Correct Option: A

   Given E_g1 = 1_eV, T₁ = 200 K, T₂ = 600 K, E_g2 =?
   

   Eg1	=	T2
   Eg2		T1

   
   Where Eg = Energy band gap
   T = Temperature
   

   Now, Eg2 = Eg1 ×	T1
   	T2

   
   

   = 1eV ×	200 K	=	1eV
   	600 K		3

   
   Hence alternative (D) is the correct choice.

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